L. L. Khalfin.

The Siberian Devonian and the Spirifer cheehiel Kon. Group

Preface

Within the fauna of Devonian brachiopods of Siberia, the greatest interest in terms of the diversity and originality of forms is presented by two groups—the genus Anathyris Peetz, on the one hand, and the group Spirifer cheehiel Kon.—on the other. I have devoted a special article (17) to the characterization of the former; the description of the group Spirifer cheehiel is the subject of the present work.

The extensive material obtained from various regions shows that the group Spirifer cheehiel in the Siberian Devonian is very widely distributed and has guiding significance for stratigraphic correlations. This alone provides sufficient grounds for becoming more closely acquainted with this group of Devonian brachiopods. Moreover, nowhere is the group Spirifer cheehiel represented so abundantly and diversely as in Siberia, and therefore its fullest study is possible only on Siberian material.

At present there is still no possibility of determining zoogeographic provinces for the Asiatic Devonian, but it may be asserted with complete certainty that, for resolving this question, the group Spirifer cheehiel will provide very important material: for the extensive area of distribution of this group, even now, in a number of cases, fairly definite boundaries can be outlined. In any case, for paleogeographic constructions this distinctive group can even at the present time provide reference points.

The group Spirifer cheehiel is a separate association of closely related species, united both by morphological features and by territorial and stratigraphic distribution, i.e., it constitutes an independent taxonomic unit, for which a more precise diagnosis must be given and genetic relations to other groups clarified.

The literature materials on the Siberian representatives of this group are extremely scanty: there is a detailed description (44) only of the Minusinsk representatives of Spirifer cheehiel, and scattered references in various literary sources to the presence of this species in the Devonian deposits of various localities of the Kuzbass, Minusinsk, and Altai.

All that has been set forth above, together with the fact that a number of extensive collections from various localities came into my possession, prompted me to write this short article on the Siberian representatives of the group Spirifer cheehiel. I was not deterred in this intention by the absence from my possession of certain literary sources, nor by the circumstance that in a number of cases, concerning broad and general topics, I could only pose particular questions but not resolve them exhaustively. The Siberian material relating to the group Spirifer cheehiel is of such considerable interest that I considered myself obliged to report it at least in the form in which this proved possible for me at the present moment.

The collections whose study formed the basis of this article were gathered by M. A. Usov (Kuzbass, Minusinsk), M. K. Korovin (Kuzbass), B. F.

Speransky (northern and western Altai), N. N. Gornostaev and P. S. Krasnopol’eva (southeastern Altai), V. A. Kuznetsov (western Altai), I. K. Bazhenov (Minusinsk), and the author of the present work (Kuzbass, western and northern Altai).

The processing of the material was carried out in the paleontological office of the Tomsk Industrial Institute named after S. M. Kirov. The photographic illustrations were prepared by A. A. Fil’bert in the photographic laboratory of the same institute.

Horizontal and vertical distribution of the group Spirifer cheehiel in Siberia.

In Siberia, three areas of distribution of the group Sp. cheehiel are known—the Kuznetsk Basin, the Altai, and the Minusinsk Basin.

The Devonian deposits of the Kuznetsk Basin, exposed along its periphery, are represented by various horizons and various facies; their brachiopod fauna has been studied better than the fauna of Devonian deposits of any other region of Siberia. Therefore, the fact that the group Sp. cheehiel has not so far been encountered along the western, southern, and eastern margins of the Kuznetsk Basin, but has been found in an enormous number of specimens along the northwestern margin of this basin, cannot be attributed to accidents of observation and collecting. The classic locality of the brachiopod group that interests us is the village of Lebedyanskoe, situated on the Mozalovskii Kitat River, near (to the west of) the Sudzhensk mines. Here spirifers of the group Sp. cheehiel occur in enormous numbers, constituting the most conspicuous element of an altogether very rich and diverse brachiopod fauna. Their mass development is accompanied by a diversity of species composition: in the Lebedyansk Devonian this group is represented by seven different forms. In general, in terms of the number and diversity of representatives, the Lebedyansk Devonian appears, evidently, to be a locality of the group Sp. cheehiel unique in its kind.

South and southwest of the village of Lebedyanskoe, spirifers of the group under consideration have been found at a number of points along the northwestern margin of the Kuznetsk Basin. Krasnopol’skii (22, 63) indicated the presence of Spirifer cheehiel in the vicinity of the village of Talovskoe in the upper reaches of the Yaya River (about fifteen kilometers southeast of Taiga station), and later (23, 11, 77) cited Sp. cheehiel from a number of points along the Ya River, partly in association with Upper Devonian forms. Prof. Korovin indicated the presence of this species on the Tom River in Devonian deposits bordering the productive series of Kuzbass (21, 32). Farther to the southwest, along the Strel’naya River and its tributaries, deposits of interest to us are also present; as early as Venyukov pointed (51, 82) to the presence of Spirifer cheehiel in interbeds of reddish limestones among green clay shales near the village of Terekhina on the Strel’naya River; in the Zarubinskii district, spirifers of this group were found by Tyzhnov (45, 17, 19) near the village of Zarubina on the Strel’naya River and along its tributary—the Bol’shoi Kurlyak.

Thus, a picture emerges of the widespread distribution of the Spirifer cheehiel group in Devonian deposits of the corresponding age along the northwestern and northern margins of the Kuznetsk Basin and adjacent areas. Along the eastern and southern margins of Kuzbass there are no marine Middle Devonian rocks, and this explains the absence there of the group Sp. cheehiel. The situation is different on the southwestern margin, where, according to Petts (35, 296), Givetian deposits are widely distributed; however, the spirifer group that interests us is completely absent from their fauna. To ascertain the reason for the absence of the group Sp. cheehiel in this locality at the present time seems hardly possible; an explanation of this circumstance by facies causes cannot be acـ

understandable, since Sp. cheehiel, as we shall see below, is widely distributed in various facies. It seems to me that the solution of the question will be found by revising the age of the corresponding deposits; the long list of forms given by Petz (35, 297–298) abounds in Upper Devonian species, with a large number of forms common to the Eifelian and Givetian stages and with the absence of reliable guide forms of the Stringocephalus horizon: the Stringocephalus burtini cited in the list is accompanied by a question mark, and on the question of the age of this fauna Petz writes: “Only this one species [Str. burtini. L. Kh.] could decide the question of the age of the entire bed, but, unfortunately, no special significance can be attached to the determination of this species, since the only specimen at my disposal is not complete, but is represented only by one dorsal valve, and moreover even this valve is not sufficiently well preserved” (35, 298). It seems to me that the fauna cited in this list comes from horizons of different ages.

Over a considerably larger area than in Kuzbass, Devonian deposits with Sp. cheehiel are developed in the Altai.

For a number of years I have been engaged in the study of the Devonian fauna of the Altai, and during this time I have had the opportunity to become acquainted with a large number of collections originating from numerous localities in this region. On the basis of this acquaintance with the Devonian fauna of the Altai, I come to the conclusion that in the Altai there are no Upper Givetian deposits which, in their brachiopod facies, would not contain spirifers of the Sp. cheehiel group.

Already in the works of Chikhachev, Shurovsky, and Helmersen, Spirifer speciosus is recorded from the Middle Devonian deposits of Rudny Altai—the form most closely related to Sp. cheehiel among European spirifers. A reliable indication of the presence of Spirifer cheehiel together with Atrypa reticularis and Cyathophyllum cf. caespitosum in the Altai was made by Pilipenko (37, 96) for the Devonian deposits of the Korgon Range (western Altai). Nekhoroshev described a section of Devonian deposits with the fauna Sp. cheehiel along the Chuya River, below the mouth of the Berdybash River (29, 63).

In northern Altai, Givetian deposits with the cheehiel fauna are developed in the basin of the Peschanaya River near the village of Kuyagan. Here, in the upper reaches of the Malafeev Creek, a tributary of the Gremishka River, which flows from the left into the Peschanaya River above the village of Kuyagan, and in the upper reaches of the Bolshaya Tikhaya River, the Devonian deposits contain, along with other brachiopods, numerous representatives of the Sp. cheehiel group.

In western Altai this group has been found by a number of Siberian geologists in deposits forming part of the northern slope of the Korgon Range; the best section of these deposits is on the Korgon River (a tributary of the Charysh River), above the quarry in which variegated and beautifully colored acid effusives, also of Middle Devonian age, were extracted as ornamental stones.

Finally, in southeastern Altai, in the upper reaches of the Chuya River and along its tributaries, an abundant cheehiel fauna was discovered by N. N. Gornostaev and collected by P. S. Krasnopeeva.

It can hardly be doubted that with further geological investigations in the Altai the number of localities of the cheehiel fauna will be multiplied, but the available materials are already sufficient to assert that the Givetian basin which covered the territory of the Altai was inhabited by a fauna in which the Sp. cheehiel group played a prominent role.

The Minusinsk fauna with Spirifer cheehiel has long been known; in 1886 it was described by Stuckenberg. In this fauna the Sp. cheehiel group is present in an enormous number of specimens and is found everywhere limestones of the corresponding age are developed. The classic locality—

... its occurrence is the village of Beiskoe, about 100 kilometers southwest of Minusinsk, and after this village the fauna received the name “Beisk fauna.”

Turning to the Givetian deposits developed west of the Minusinsk–Kuznetsk–Altai region, we must first of all note the disappearance of the Spirifer cheehiel group already in Kazakhstan. The fauna of the Givetian deposits of Kazakhstan, unfortunately, has not been described, but the detailed lists of forms from these deposits given by Kassina (15, 78—90) do not contain the group of brachiopods that interests us. Likewise, this group is absent in Turkestan and in the Urals, and still more so in Europe. In rough approximation, the western boundary of the distribution of the cheehiel fauna may be considered the 80th meridian east of Greenwich.

It is extremely difficult to say anything definite about the distribution of the cheehiel fauna east of the Minusinsk depression, since the Devonian fauna of Eastern Siberia and the DVK has been studied quite inadequately—or rather, has not been studied at all. Scattered data on the Devonian deposits of these regions have been summarized in Krish tofovich’s review of the geology of the countries of the Far East (24, 81—89), but there are no indications whatever of the presence of Sp. cheehiel in the Givetian deposits of these regions. The same applies to the Devonian deposits of Mongolia.

In the literature available to me there are no sufficiently detailed indications concerning the distribution of the Spirifer cheehiel group beyond the borders of Siberia.

The first specimens of Sp. cheehiel, described by Koninck and Kayzer, came from China, but were acquired by travelers in Shanghai pharmacies, since in China fossils were ascribed medicinal properties. Grabau (10, 162) notes that “Spirifer cheehiel—typical Chinese form,” and Krish tofovich writes (24, 270) that “in the Middle Devonian a distinctive fauna with such a representative as Sp. cheehiel develops in the Chinese basin,” but these authors give no data on the horizontal distribution of this species in China. However, accepting the Givetian age of this form, one may make use of Grabau’s statement that deposits of this stage (Kütsing group) are distributed in eastern Yun-Nan, eastern Guang-Xi and southern Hu-Nan (10, 191), as well as of the paleogeographic map of the Givetian epoch in China (10, 160), on which Grabau depicts the Givetian basin as a bay of the Himalayan geosyncline, encompassing only the southeastern provinces. Thus, on this map there is no direct connection between the Givetian basin of China and the Kuznetsk–Altai basin, and they are separated by an extensive landmass.

A direct indication of the presence of Sp. cheehiel in the Givetian deposits of Yun-Nan is found in the work of Fromaget and Saurin (8, 318).

In Kayser’s old work there is, with reference to Koninck, an indication (20, 88) of the presence of Sp. cheehiel together with Strophalosia productoides Murch. in the Devonian deposits of Cape Van Diemen (Melville Island), but I have been unable to find either the original sources or later confirmations of this highly interesting report, and therefore I cannot make use of it further.

In America Sp. cheehiel has not been found.

Thus, two basins inhabited by a fauna with Sp. cheehiel are outlined—the Minusinsk–Kuznetsk–Altai and the South Chinese.

The vertical distribution of the Sp. cheehiel group is very limited and is confined within the limits of the Givetian stage. The species Sp. cheehiel has a Givetian age in China (8, 318). In Siberia the position of this group is determined quite precisely in the section of the Givetian–Frasnian deposits in northern Altai according to Malafeev’s key (18); in this section the following sequence of beds occurs:

The group Sp. cheehiel occupies exactly the same position in the Kuzbass. Therefore there is every reason to assert that the group Sp. cheehiel in Siberia has a guiding significance for the Upper Givetian deposits, being the stratigraphic analogue of the species Stringocephalus burtini.

In some older works, for example in Petz (36, 189), Sp. cheehiel is listed together with the guiding Upper Devonian forms. There is no doubt that in a number of cases this is explained by a mixing of forms from different horizons as a result of non-bed-by-bed collections of fauna. However, A. V. Tyzhnov has made an oral communication to me that he encountered small representatives of the Sp. cheehiel group in the very lowest beds of the Frasnian deposits of the Kuzbass, and I have every reason to treat with complete confidence the testimony of this attentive observer and expert on the Devonian of the Kuzbass. Cases of the appearance of spirifers of the group that interests us at the base of the Frasnian stage are exceptional; they do not change the general state of affairs and do not deprive the Sp. cheehiel group of its guiding significance. We shall return later to the facts established by A. V. Tyzhnov.

On the biogeographic relationships between Spirifer cheehiel Kon. and Stringocephalus burtini Defr.

It was noted above that west of the Kuznetsk-Altai region the cheehiel fauna has not been encountered. The disappearance of the group Spirifer cheehiel is accompanied by the appearance in its place of Stringocephalus burtini, this most characteristic species for the Givetian deposits of Kashgaria, Turkestan, the Urals, and Europe.

This circumstance deserves attention, since it may be used for the Givetian geography of Eurasia.

The factual side of the question is as follows. In the Givetian deposits widely distributed in the Altai, spirifers of the group Spirifer cheehiel are found everywhere in large numbers, but up to now not a single specimen of Stringocephalus burtini has been found. This species is also absent in the Minusinsk Devonian. In the Kuzbass, the Givetian brachiopod fauna is richly and diversely represented in the vicinity of the village of Lebedyanskii, but among the seventy-five species of Lebedyanskii brachiopods known to me, Stringocephalus burtini is absent. It has likewise not been found at other localities of the Kuzbass; the sole exception is the Givetian deposits of the village of Iganino on the Kara-Chumysh River (southwestern margin of the Kuzbass), whence Petz described one dorsal valve which he assigned, with a question mark, to Stringocephalus burtini.

In general, indications of the presence of Stringocephalus burtini in the Devonian deposits of the Asiatic part of the USSR east of the 80th meridian are very rare and extremely uncertain. These are either the already mentioned dorsal valve from the Kuzbass, whose “character of the beak is such that the form can more likely be assigned to Enantiosphen” (35, 171), or an “internal mold, somewhat recalling S. burtini” from Tarbagatai (50, 1071), or “sections of shells visible in the rock, recalling S. burtini” in the Far East (24, 84).

Even if it be admitted that the dorsal valve from the Kara-Chumysh River really belongs to the species S. burtini, i.e., that in the Givetian basin of Kuz—

single representatives of this species entered the basin, nevertheless this in no way bears comparison with those stringocephalid banks that are described, for example, by Nalivkin for the upper horizons of the Middle Devonian of Turkestan, and which are dense limestones packed with shells of S. burtini, at times of gigantic size (28, 151). At the same time, in the Lebedyan Devonian, with S. burtini completely absent, spirifers of the Spirifer cheehiel group enjoy enormous distribution and great diversity; their shells entirely fill certain limestone beds. An analogous picture is observed in Minusinsk and in the Altai.

From these relationships we are entitled to conclude that, for the territories under consideration, Stringocephalus burtini and Spirifer cheehiel are antagonists, since the presence of one of them excludes the presence of the other. This essential circumstance requires explanation. It cannot be explained by assuming that these species characterize different facies of a single basin: spirifers of the Sp. cheehiel group are distributed in very different facies. This assumption is all the more impossible because, as we shall see below, in southeastern China both of these forms occur together. There remains only one explanation: faunal exchange between the Kuznetsk–Altai and Middle Asian basins in Givetian time was impeded; these basins, if not completely isolated, in any case had extremely limited communication. That is, for the Givetian deposits of the territories under consideration we can establish the presence of two faunas that existed in parallel but were spatially separated—the cheehiel fauna and the stringocephalus fauna.

However, in the South Chinese Givetian basin we observe a mixing of these faunas: there, alongside Spirifer cheehiel, occur Stringocephalus burtini (in the shales of Kuahsinshan) and Stringocephalus obesus Grab. (in the limestones of Tungshan). This fact, it seems to me, can have only one explanation: the South Chinese basin communicated both with the Kuznetsk–Altai basin and with the Middle Asian one, and was colonized by fauna migrating from both. In this case such forms as Spirifer cheehiel and Emanuella takwanensis must be regarded not as “typically Chinese,” but as typically Siberian, since the fauna apparently migrated mainly from the Kuznetsk–Altai basin into the South Chinese basin, and not the reverse; otherwise it is unclear why, together with Spirifer cheehiel, Str. burtini—this cosmopolitan, which possessed the capacity for wide dispersal—did not penetrate from the South Chinese basin into Siberia.

The conclusions at which we have arrived from considering the geographical distribution of the cheehiel fauna are not unexpected, and merely confirm and specify the available data on Givetian paleogeography. Thus, on the one hand, the absence of marine Givetian deposits in the northern arcs of the Tien Shan is a fact established by many investigators; on Arkhangelsky’s paleogeographic map (2, 121) an extensive island is shown here, separating the Kazakhstan–Altai basin from the Turkestan one; for the Givetian epoch this land, apparently, must be regarded as part of an extensive continent. In addition to the isolation of the Siberian basin from the Turkestan basin, the former was hardly likely, in the Givetian epoch, to have had broad and direct communication with the Ural basin either; that is, the existence in the Middle Devonian of an extensive land area between these basins (Tobolskia according to Grabau) seems to me entirely probable.

On the other hand, the idea of communication between the Minusinsk Givetian basin and the Chinese one was definitely expressed by Grabau (10, 162), and above we have seen that analysis of the fauna compels us to assume direct communication between these basins, and not a roundabout one through Turkestan, although this

assumption, as it were, and is in contradiction with the existence of land within the Gobi throughout the entire Devonian. We shall dwell on these questions in greater detail in the last chapter of the present work.

General characterization of the cheehiel fauna of Siberia.

The richest and most varied, and at the same time the most thoroughly studied, is the cheehiel fauna of the village of Lebedyanskoe (northern margin of Kuzbass). Here, in addition to brachiopods, coelenterates and bryozoans are very widely distributed; mollusks and trilobites are considerably less numerous. The brachiopods of this fauna have been described by me, the corals by Radugin (19, 38); the remainder of the fauna has not been worked up.

Within the brachiopod fauna of the village of Lebedyanskoe, 75 forms have been established. The largest percentage (37%) consists of new forms, besides which this fauna contains a further 7 forms that are specifically Asiatic (Chonetes subcancellata Reed, Uncinulus subsignatus Reed, Spirifer martianoffi Stuck., Spirifer cheehiel Kon., Spirifer cheehiel alata Stuck., Athyris trapezoidalis Peetz, Atrypa sinensis Kays.). European forms play a very large role (30.9%) in the Lebedyanskoe fauna, which is characteristic of the Devonian fauna of Asia in general; this circumstance has led some authors to suppose a current of European fauna into Asia throughout the entire Devonian period. For the Givetian basin of Siberia one cannot agree with this assertion, and, as will be seen below, the abundance of European forms in the composition of the cheehiel fauna of Siberia has another explanation. American species in the Lebedyanskoe fauna make up 13.8% and are represented by such characteristic forms as Spirifer mesocostalis Hall, Athyris fultonensis Swall., Meristella nasuta Conr., Schuchertella chemungensis Conr., Rhipidomella vanuxemi Hall, and others. 7.5% are forms that are universally distributed, namely: Leptaena rhomboidalis Wilck., Schizophoria striatula Schl., Spirifer undifer Roem., Atrypa reticularis L., Atrypa desquamata Sow.

The brachiopods of the Lebedyanskoe Devonian are distributed among 14 families, with the families Spiriferidae and Athyridae being most richly represented; to these belong 44% of all species of the Lebedyanskoe fauna.

The various species of brachiopods in the Lebedyanskoe fauna are far from equally distributed. The following are present in mass development: Leptaena rhomboidalis Wilck., Schellwienella umbraculum Schl., Dalmanella eifeliensis Vern., Schizophoria striatula Schl., Uncinulus korovini Khalf., the group Sp. cheehiel, Athyris subacuminata Khalf., Atrypa reticularis L., Atrypa desquamata Sow. Also very numerous are the productids, Stropheodonta asella Vern., Rhipidomella vanuxemi Hall, Delthyris altschedatiensis Kor., Athyris concentrica Buch, Athyris circularis Khalf., the genus Retzia, Atrypa tubaecostata Paeck. In contrast to the cheehiel fauna of the Altai and Minusinsk, Spirifer martianoffi Stuck. is rarely encountered in the Lebedyanskoe fauna.

The group Spirifer cheehiel in the Lebedyanskoe fauna is represented by seven forms, which have been described in detail by me in the article on the Lebedyanskoe fauna. Since this article has already been awaiting publication for two years, I consider it not superfluous to borrow from it brief characteristics of these forms.

Spirifer cheehiel Kon. (pl. I, fig. 1a–c). The outlines of the shell are variable, usually subtriangular, more rarely trapezoidal or semi-elliptical; the ratio of width to length is 2–2.5, rarely less than two. The area of the ventral valve is well developed; in specimens moderately developed in width it has a triangular character, in winged forms it is bounded by almost parallel margins. The area of the dorsal valve is 1–1.5 mm high, about 5–6 times lower than the area of the ventral valve. The saddle and sinus are normally developed—

are developed, rounded. The sizes of the specimens range from 18 to 100 mm in width.

Spirifer cheehiel Kon. var. alata Stuck. Differs from the typical form in its greater development in width: the ratio of width to length is close to 3.

Spirifer biderveхus Khalf. (pl. I, fig. 2a–b). The outlines of the shell are trapezoidal; the ears are small, but distinctly delimited; the ratio of width to length is less than 2. The structure of the areas is the same as in Sp. cheehiel. The sinus is normally developed, with a rounded bottom, but the saddle is constructed differently than in Sp. cheehiel: it is roof-shaped, sharply crested; its sides are not smooth curved surfaces, but almost planes converging at an angle of about 80° (near the anterior margin).

Spirifer mesolobus Korovin (pl. I, fig. 3). The outlines of the shell, the ratio of width to length, the structure of the areas, and the character of the saddle are as in Sp. cheehiel. But in the sinus there is a broad median ridge, appearing at a distance of 1/3 or even 1/2 of the shell length from the beak and reaching near the anterior margin the width and height of the radial folds adjoining the sinus.

Spirifer semicostalis Khalf. (pl. I, figs. 4, 5). This species in all respects resembles Sp. cheehiel, but in the sinus there is a very thin riblet, beginning at the very beak and traceable to half the length of the shell, gradually weakening and completely disappearing in the anterior part of the sinus; thus, this riblet has an entirely different character from the ridge of the preceding species.

Spirifer mirabilis Khalf. (pl. II, fig. 8a–b). Differs in the hypertrophied development of the saddle and sinus. The sinus is very deep and reaches an extraordinary width near the anterior margin; the tongue is extraordinarily developed: its height almost equals the length of the sinus from the beak to the frontal margin; the tongue has the outlines of an isosceles triangle with an angle of 45° at the apex. The bottom of the sinus is rounded in the umbonal part, flat near the anterior margin; within the limits of the tongue a short and broad, weak swelling gradually appears on it, disappearing again at the apex of the tongue. The saddle is narrow, compressed laterally, very high, sharp-crested. The areas are as in Sp. cheehiel. The ratio of width to length is about 3. Dimensions—about 90 mm in width.

Spirifer orthogonalis Khalf. (pl. II, fig. 9a–b). The only species in which the length of the hinge margin is somewhat less than the greatest width of the shell. Because of this the outlines of the shell are subrectangular, with straight cardinal angles. The ratio of width to length is about 1.6. The area of the ventral valve is only slightly higher than the area of the dorsal valve. Saddle and sinus as in Sp. cheehiel.

All these forms possess the same sculpture characteristic of Sp. cheehiel. Of them only Sp. cheehiel is massively developed in the Lebedyanian fauna; the other forms are ordinary but occur more rarely, and Spirifer mirabilis has been found in a single specimen.

The coelenterates of the Lebedyanian Devonian were studied by Radugin (38). He described 48 forms: 20 of them belong to Rugosa, 20 to Tabulata, and 8 to Stromatoporoidea. This fauna is striking in its peculiar character: of the 48 forms, 31 are new; in particular, Radugin established two new genera—Natolophyllum and Neoroemeria. In general, the coral horizons of the Lebedyanian Devonian lie below the brachiopod horizons, but, analyzing the coelenterate fauna, Radugin comes to the conclusion that it is of Zhivetian age and only for the very lowest parts of the Lebedyanian Devonian admits the possibility of an Upper Eifelian age.

In the Altai the cheehiel fauna is less studied, but it has been precisely established that it has the same character.

In the Northern Altai, spirifers of the Sp. cheehiel group are fairly numerous in the Givetian deposits and at times reach gigantic dimensions—up to 140 mm in width. The North Altai Sp. cheehiel (Pl. III, figs. 13–15; Pl. IV, figs. 23, 27) are in all respects similar to the Lebed’ specimens, but the internal molds of the ventral valves in the former show the following features: the muscular boss in the Altai specimens is divided by a deep and narrow depression, whereas in the Lebed’ specimens its surface is almost even and has only a very weakly expressed, broad and flat depression (Pl. III, figs. 16–18). This difference is so constant in all specimens, both large and small, that I consider it necessary to distinguish the Altai forms as a certain local variety—Sp. cheehiel n. var. altaica. In addition to this form, Spirifer cheehiel var. alata is present in the Givetian deposits of the Northern Altai; some internal molds of dorsal valves, with their compressed from the sides, sharp-topped saddle, very much resemble Spirifer bidevexus or Spirifer mirabilis, but the material is insufficient for final determinations.

Together with the spirifers of the Sp. cheehiel group, the following forms occur:

Productella spinulicosta Hall.
    “ arctirostrata Hall.
Dalmanella sibirica Khalf.
Schizophoria striatula Schl.
Cyrtina heteroclita Defr.
Spirifer cf. cabedanus Vern. et Arch.
Fenestellidae,
crinoid columnals,

and in higher beds, where spirifers of the Sp. cheehiel group are very rare, Spirifer mesocostalis Hall, Spirifer mucronatus Hall, Atrypa reticularis L., Stropheodonta asella Vern., Liorhynchus kellogi Hall, and others appear in large numbers. In the overwhelming majority these forms are common with the Lebed’ fauna.

From the Western Altai (Korgon Range) I have a small collection of Givetian brachiopods, among which there are several specimens of typically expressed Spirifer cheehiel (Pl. III, fig. 21), as well as Spirifer cheehiel var. altaica (Pl. III, fig. 20). They are associated with the following brachiopods: Leptaena rhomboidalis, Schellwienella umbraculum, Schizophoria striatula, Dalmanella eifeliensis, Uncinulus korovini, Atrypa reticularis, and others; the most widespread form is Spirifer martianoffi. In the Korgon \(D^2_2\), cyrtospiriferids are very numerous; pelecypods occur rarely (Conocardium cuneus Hall, Cypricardinia lima Schnur).

In the Southeastern Altai our spirifers constitute a very widespread group in the Givetian fauna. In addition to typical Sp. cheehiel (Pl. II, fig. 6), Spirifer semicostalis (Pl. II, fig. 7), Spirifer mesolobus (Pl. IV, fig. 28), and a certain form have been found in the Southeastern Altai, the most important distinctive feature of which is the unusual inflation of the shell. In a number of characters this form stands closest to Spirifer bidevexus; in particular, it has the same character of the saddle, the same trapezoidal outline of the shell, and the same number of ribs (6–7 on each side of the saddle and sinus). But the dorsal valve in the Altai form is extremely convex and the saddle is very high; the general character of the convexity of the dorsal valve is roof-shaped. The ratio of the width of the shell to its thickness, even in the most inflated specimens of Sp. bidevexus, is always greater than two, and usually about three; in the Altai species, however, it is close to 1.5. The degree and character of the convexity of the dorsal valve in our species bring it closer

distinguish it by its general habitus from such species as Spirifer acuminatus Conr. and Spirifer cultrijugatus Roem., differing, however, in the length of the hinge margin, the character of the areas, and the number of ribs. This Altai form evidently must be separated as a distinct species, which may be named Spirifer cultrijugatifomis (pl. V, fig. 35a–e); on pl. V, figs. 34, 35a, 36 are given, for comparison, images in one projection of shells of Spirifer bidevexus, Spirifer cultrijugatifomis, and Spirifer cultrijugatus.

Together with Sp. cheehiel in southeastern Altai, rather diverse brachiopods have been found—Leptaena rhomboidalis, Schizophoria striatula, Dalmanella sibirica, Productella spinulicosta, Productella productoides, Athyris concentrica, Atrypa reticularis, and others; representatives of the species Spirifer martianoffi Stuck. are also very numerous, as in the Korgon fauna.

The Givetian fauna of the Minusinsk Basin was described by Stuckenberg; using this description and the small collection available to me, I can give the following characterization of this fauna.

The most widespread species are Spirifer cheehiel and Spirifer martianoffi. The first is represented by the typical form and by the variety alata; there is also Sp. bidevexus. Further, in this fauna occur Retzia lopatini Stuck., Emanuella takwanensis Kays., Athyris concentrica Buch, Spirifer schmidti Stuck., Atrypa reticularis L., productellids, a certain species of the genus Schuchertella or Streptorhynchus (“Streptorhynchus crenistria” of Stuckenberg), and also Crania obsoleta Goldf. More detailed lists of the Minusinsk Devonian fauna are given in Edelstein’s summary (7, 26).

Comparing the Givetian fauna from all the regions considered above, we must first of all note that this fauna is uniform in all these regions, being connected not only by the presence of a peculiar group of spirifers, but also by a large number of other forms. Further, in this fauna there is a large number of endemic forms—up to 30% and more in various regions. But alongside this, a very large percentage of forms in the Siberian cheehiel fauna consists of European forms; moreover, the influence of the American fauna is noticeable as well. Important for our further reasoning is the absence in the cheehiel fauna of such a typical Givetian form as Stringocephalus burtini, and also Uncites gryphus.

Along with these features of similarity in the cheehiel fauna of the various regions, we must also note the existing differences, which in general are insignificant and should apparently be explained by facies causes. Thus, Sp. martianoffi, very numerous in southeastern Altai, in the Korgon Range and the Minusinsk Basin, is very rare in the Lebedyanka Devonian and is completely absent in the Devonian of northern Altai (the Malafeev key). Schellwienella umbraculum is widely distributed in the Lebedyanka, in the Korgon Range, and has not been found at other points. Schizophoria striatula is absent in the Minusinsk Basin, etc. A complete comparison from this point of view of the fauna of all regions is impossible until it has been fully studied, but to illustrate the existing differences one may give the following table of distribution of the most common forms:

That these differences depend on differences of facies is also confirmed by the character of the corresponding deposits and by the fauna. Thus, the abundance of bryozoan horizons, the variegated alternation of sandstones, argillites, limestones, and marls, as well as the presence of coral horizons in the Lebedyan Devonian, indicate that here we are dealing with deposits of a shallow and unstable marine basin. In southeastern Altai the cheehiel fauna is enclosed partly in the cement of a conglomerate, partly with pinkish-colored rock. On the contrary, in northern Altai this fauna is contained in a monotonous clayey-schistose sequence with rare interbeds of very fine-grained sandstones; here benthogenic limestones and colonial tabulates are entirely absent; even solitary corals (Zaphrentidae) occur only in a few higher stratigraphic horizons, in which a certain shallowing of the basin is already felt; evidently these are deposits of a sufficiently deep and stable basin. In southeastern and western Altai, horizons with the cheehiel fauna are interbedded with flows of effusives and, naturally, contain an admixture of tuffaceous material; in northern Altai effusives are completely absent from the composition of the Givetian rocks. All this permits us to say that the group Spirifer cheehiel occurs in a rather varied facies setting and, in particular, is a eurybathic group: these spirifers inhabited zones of the sea from the nearshore, wave-swept zone to a zone deeper than that of solitary corals; this group attains its greatest distribution in deposits of shallow marine basins.

I am unable to compare the cheehiel fauna of Siberia with that of southeastern China; I shall note only the most important difference: in the composition of the cheehiel fauna of China, Str. burtini is widespread, whereas it is absent in Siberia.

The abundance in the Siberian cheehiel fauna of European forms, at first glance, is in contradiction with what was stated above, when considering the relationships between Sp. cheehiel and Str. burtini, namely with the considerations on the isolation of the Givetian basin of Siberia from the Ural and Turkestan basins (and consequently from the European as well). However, a closer consideration of the European forms present in our fauna gives an exhaustive explanation of this seemingly paradoxical circumstance.

If we take the best-studied of our faunas—the Lebedyan—then in it we shall find the following European forms:

Productella subaculeata Murch.
Strophendonta asella Vern.
Leptaena rhomboidalis Wilck.
Schellwienella umbriculum Schl.
Dalmanella eifeliensis Vern., typ. et var.
Schizophoria striatula Schl.
Spirifer cabedanus Vern. et Arch.
Spirifer undiferus Roem.
Spirifer robustus Barr.
Spirifer aviceps Kays.
Cyrtina heteroclita Defr., typ. et var.
Merista plebeia Sow.
Merista lacryma Sow.
Athyris concentrica Buch.
Athyris rugata Dav.
Athyris glassi Dav.
Athyris gracilis Sandb.
Anathyris phalaena Phill.
Anathyris helmersenii Buch.
Atrypa reticularis L.
Atrypa desquamata Sow.
Atrypa tubaecostata Paeck.

Let us consider the vertical distribution of these forms. Pr. subaculeata is already known in the lower half of \(D_2\) of Siberia (35, 128; 5, 1205), and also in Europe. Stropheodonta asella occupies in Siberia a lower position than in the European part of the USSR, where it characterizes the lower horizons of \(D_3\), whereas in Siberia it occurs both in \(D_2^2\) and in \(D_3^1\). L. rhomboidalis appears already in the Upper Silurian. Schellwienella umbraculum is undoubtedly known from the Eifelian stage, as are Dalm. eifeliensis and Sch. striatula; in particular, all these forms are distributed in the Eifelian limestone of Padaukpin, Burma (39, 141). Spirifer cabedanus in Spain and France is known from the cultrijugatus beds (35, 84); Mansuy described it from deposits with Sp. tonkinensis of Indochina (26, 40), to which a Coblenzian age is now assigned (8, 317). Spirifer undifer is “almost exclusively a Stringocephalus form” (43, 64), but there are indications (Barrois, Chernyshev) of its presence also in the Eifelian stage; in the Minusinsk Basin Sp. undifer is distributed in horizons lying below the beds with Sp. cheehiel. Sp. robustus is distributed chiefly in the Lower Devonian and the Eifelian stage (28, 115). Cyrtina heteroclita is likewise known from the Lower Devonian. Merista plebeia is a form, like Sp. undifer, predominantly Givetian, but Gürich found this species in Eifelian deposits of Poland (11, 268), Reed described it from the calceola beds of Burma (39, 113), and apparently this species occurs still lower in France (33, 25). Merista lacyrma is distributed in Givetian deposits, rising into \(D_3\), but Reed described from the Padaukpin limestone, under the name Mer. aff. lacyrma, a form scarcely distinguishable from this species. Athyris concentrica is known from the Lower Devonian. Ath. rugata and Ath. glassi have been found in the Stringocephalus deposits of England¹. Athyris glacilis occurs in similar deposits of Germany. An. phalaena in Europe occurs in the Lower and Middle Devonian; An. helmersenii has hitherto been known only from Givetian and Frasnian deposits of the USSR. Atr. reticularis is distributed from the Upper Silurian. Atr. desquamata is undoubtedly known from the Eifelian stage, and finally, Atr. tubaecostata occurs in the upper parts of the Middle and in the lower parts of the Upper Devonian of Europe.

From the review presented it is evident that, of the 22 European forms of the Lebedyan Devonian, 15 species are not characteristic solely of the Givetian stage, but also occur in lower horizons; i.e., these forms could have penetrated into the Kuznetsk–Altai basin as early as the Eifelian epoch. To the same category we should apparently also assign Mer. lacyrma. Of the remaining seven species, special mention must be made.

The horizontal and vertical distribution of A. rugata, A. glassi, and A. gracilis cannot be considered definitively limited to the Stringocephalus stage: they are very close to A. concentrica—a species to which, until comparatively recently, a number of authors ascribed a very broad, collective meaning, including within it many closely related species. The same must be said of Atrypa tubaecostata: until 1913, specimens belonging to this species were described under the names A. reticularis or A. aspera. An. helmersenii belongs to a genus whose vertical distribution still remains a puzzle: in Siberia representatives of this genus appear at the very top of the Middle Devonian, chiefly in \(D_3^1\), whereas in Europe they were rather widely distributed in \(D_1\) and \(D_2\); there is no doubt that, having emigrated from Europe, the anathyrids existed somewhere throughout the whole of the Middle Devonian. There remains only Str. asella, whose vertical distribution in Siberia does not coincide with that in Europe; therefore in the present case a doubt arises whether—

whether the Siberian Middle Devonian stropheodonts are in fact genetically identical with the European Upper Devonian ones, and whether here there is only a convergent resemblance carried to an extreme degree. To this it must be added that, with the exception of A. tubaecostata and S. asella, all our other forms, whose presence in the Eifelian deposits at the present moment cannot be proven, occur in the Lebedyansk fauna as single specimens, whereas the majority of the other species in the list under discussion enjoy mass development in this fauna or are very widely distributed.

If we now recall that in the Siberian cheehiel fauna such popular Givetian forms as Str. burtini and Unc. gryphus, already distributed in Kashgaria and Turkestan, are absent, then we shall be entitled to draw the conclusion following from all the preceding arguments: the similarity of the Givetian Lebedyansk fauna to the European one is inherited from the Eifelian epoch; the absence in this fauna of such widespread Givetian forms as Str. burtini and Uncites gryphus, together with the abundance of endemic species and especially of the group Sp. cheehiel, indicates that in Givetian time the influx of European forms into the Siberian basin from Europe and Turkestan had ceased, i.e. that the former in Givetian time was isolated from the latter.

Everything said with regard to the Lebedyansk fauna may be extended to the entire cheehiel fauna of Siberia, since it was shown above that this fauna is uniform and subject only to insignificant local variations of a facies character.

The solution of the question of the routes by which the Turkestan-European fauna penetrated into the Eifelian Siberian basin is not part of the task of this article, and it is hardly possible at the present time, given the poor state of study of the Siberian Eifelian fauna. I shall note only the striking abundance of common forms in the Givetian brachiopod fauna of the village of Lebedyanskoye and in the Eifelian fauna of the Padaukpin limestone of Burma, which can be seen quite clearly from the following table:

¹) Str. interstrialis, var. birmanica Reed.
²) Kayserella lepida Schnur?
³) Atr. reticularis var. desquamata Sow.?
⁴) Meristella? aff. lacryma Sow.

On the systematic position and genetic relationships of the group Sp. cheehiel

The abundant and varied Siberian material belonging to the group Spirifer cheehiel makes it possible to express certain considerations on the systematic position of this group and its genetic relationships to closely related forms.

The assignment of the brachiopod group under consideration to the genus Spirifer Sow. s. lato can, of course, raise no doubt. But, constituting a fairly well characterized and distinct association of forms, this group deserves to have a definite place assigned to it within this extensive and diffuse genus. In approaching this question, we must first of all establish the diagnosis of this group of spirifers.

The shell is of considerable and large size, developed in width, and of strongly varying outline—semi-elliptical, subtriangular, trapezoidal. The hinge margin, with rare exceptions, constitutes the greatest width of the shell. The area of the ventral valve is well developed along the entire hinge margin, but is not high: usually in fully adult individuals it does not exceed 5–7 mm; in specimens moderately developed in width, the area has the outline of a triangle, though strongly elongated at the base; in specimens strongly elongated in width, however, the triangular outlines of the area are preserved only near the plane of symmetry, while throughout the rest of its extent it is bounded by almost parallel margins; the beak of the ventral valve is curved. The area of the dorsal valve is considerably lower: 1–1.5 mm. Only in Sp. orthogonalis does the area of the ventral valve exceed the area of the dorsal valve little in height. The areas of the ventral and dorsal valves form a dihedral angle of 50°–70°. The well-preserved surface of the area of the ventral valve bears several sharp longitudinal lines and fine, intermittent, somewhat nodular transverse riblets (Pl. IV, figs. 29, 30). The sculpture of the areas is entirely analogous to that in the species Spirifer audaculus Conr., judging from the illustration given in the monograph of Hall and Clarke (13, pl. XXIV, figs. 10, 11). The delthyrium is a broad triangle, the length of whose base is almost twice its height; in the upper part the delthyrium is covered by a convex deltidial plate of fairly complex structure (Pl. IV, fig. 30). The process of deposition of the substance of the deltidial plate, so far as can be judged from our material, proceeded in the following manner: initially two low plates are deposited (a′—a″ in fig. 30), bordering the delthyrium in its upper part and situated almost at a right angle to the surface of the area; then the delthyrium begins to become overgrown from the sides and partly from above, which leads to the formation of the deltidial plate proper (b); in this process, often (and possibly always) a round opening (c) forms in the middle of this plate, which, however, is subsequently filled by an additional deposition of lime; traces of this overgrown opening are observed rather often, but I have not seen a single specimen in which it remained open, although Koninck observed it in such a state in a Chinese specimen of Sp. cheehiel. The area of the dorsal valve is furnished with a notothyrium.

The saddle and sinus begin at the very beaks, are well developed, and have various features in different species.

The sculpture consists of broad, flat radial folds, numbering from 6 to 10 on each side of the saddle and sinus. The spaces between the folds are narrower than the folds themselves, but vary considerably even among representatives of a single species: sometimes they are very narrow and sharp, sometimes rounded and in width almost equal to the folds. In the sinus and on the saddle the folds are always

are absent, but in some species a median riblet or ridge appears in the sinus. The entire surface of the shell is covered with dense concentric growth marks having a lamellar character; there are 20–30 growth lamellae per 1 cm. Some of the growth marks are expressed more sharply than the others, especially near the frontal margin. When the outer layer of the shell is well preserved, the following detail of the sculpture is observed: each accretion lamella, along its free edge, is furnished with a fringe of the tiniest spines—papillae (pl. II, figs. 11, 12), directed obliquely toward the anterior and lateral margins. If the surface of the shell is slightly worn, these spines create the impression of radial striation, which, together with the concentric one, forms a fine reticulate sculpture.

Internal molds reveal the absence of a delthyrial plate and strongly developed muscle bosses of subtriangular or oval shape; their surface is covered with longitudinal or fan-shaped striation; laterally from them there are numerous punctate ovarian impressions. Dental plates are developed, but are often masked by abundant deposition of calcium carbonate along their sides; the teeth are massive and thick, entering special sockets of the dorsal valve; the structure of the hinge apparatus is shown in pl. V, figs. 33 a–b. The brachial supports were successfully prepared out and studied in detail (pl. IV, figs. 31, 32): long crura run from the points of attachment at the margins of the notothyrium toward one another and meet quite closely, approximately at half the distance between the apex and the anterior margin of the dorsal valve. Here they are joined by the primary lamellae, which diverge as they approach the anterior margin. At the junction of the crura and the primary lamellae there are well-developed jugal processes, directed ventrally. The crura have a subelliptical cross-section, the primary lamellae one close to semicircular, their convex side being turned toward the plane of symmetry and the flat side toward the lateral margins of the shell; the secondary lamellae gradually lose their semicircular cross-section and, with increasing distance from the plane of symmetry, become almost flat. Both the crura and the entire calcareous band forming the brachial spirals are hollow within. In connection with this circumstance the following additional remarks must be made: the indicated detail of the structure of the brachial apparatus was established on specimens that had undergone partial silicification. I have at my disposal several specimens in which the crura, brachial supports, and separate portions of the valves are silicified; in the case where the internal cavity of the shell is filled with crystalline calcite, after the latter is dissolved, preparations of ideal preservation are obtained (pl. IV, fig. 32), revealing the tubular character of the brachial band and the crura. However, the selective character of silicification (I have not observed a single specimen in which, for example, the dental plates were silicified) must apparently indicate that the structure, and possibly also the composition, of individual parts of the skeleton were different. Therefore the following case is theoretically possible: during the animal’s life the crura and the brachial band were not hollow, but their internal, axial part, in composition or structure, or in both respects, differed from the external, peripheral part. In that case, with selective silicification, it could have affected only the latter, and consequently the observed tubular character of the indicated skeletal elements would be a secondary phenomenon. And although, for certain reasons, this supposition seems to me unlikely, nevertheless special investigations will be required for a final solution of the question.¹

¹ At present I am engaged in studying the structure of the brachial apparatus in various groups of spirifers in thin sections.

The width of the calcareous band of the primary lamella in adult individuals is 1.5–2 mm. The number of whorls of each spiral is about 30; the apices of the spiral cones are raised toward the cardinal angles, their axes forming an angle of 100°–120°.

Such is the general characterization of the group of spirifers that interests us. On the basis of the character of their sculpture they could be assigned to the subgenus (or genus) Hysterolites in the sense in which this subgenus is now understood. It is precisely to this subgenus that the species Spirifer speciosus is also referred—a form most closely related to Sp. cheehiel. In this connection the following observations may be made: the term “Hysterolites” was used by Schlotheim 115 years ago to unite the most diverse forms, for example “Hysterolites” vulvarius (Schizophoria vulvaria), “Hysterolites” paradoxus (Spirifer paradoxus), “Hysterolites” hystericus (Spirifer hystericus), while alongside these Spirifer speciosus was called in one case Terebratulites intermedius (40, 253), and in another—Anomites terebratulites speciosus (41, 66). It is quite obvious that the term “Hysterolites” in its original interpretation in no way corresponds to the concept of a genus or subgenus, and it seems to me that Hall and Clarke were right when they warned against the use of this term (12, 213).

At the same time, the Spirifer cheehiel group represents a natural association of forms united by a number of internal and external features, and also united stratigraphically and geographically—and therefore it should also be united in a systematic respect. Most probably it would have been more correct to separate this group into a special subgenus, and only the impossibility, for me, of becoming thoroughly acquainted with the Chinese representatives of the Sp. cheehiel group, as well as with the closest European and American forms, compels me to refrain from doing so. Therefore, despite all the archaic character and uncertainty of this term, I am compelled to use the name Hysterolites, by which, as applied to our group, we shall understand a certain subgenus of the genus Spirifer Sow.

The forms closest to the spirifers of our group are the European Spirifer speciosus Schl., the American Spirifer duodenarius Hall, and the Indochinese Spirifer tonkinensis Mansui. Schpin considered Sp. cheehiel a variety of Sr. speciosus (43, 93). This point of view is supported by Fromaget and Saurin; these authors (8, 317–318) point to the presence in Indochina and Yunnan of all three forms: in the Coblenzian deposits, Sp. tonkinensis; in the Eifelian, Sp. speciosus; and in the Givetian, Sp. cheehiel. All these forms are regarded as a single genetic branch, and for them the following names are proposed:

\[ \begin{aligned} &\textit{Spirifer tonkinensis} \;—\; \textit{Spirifer speciosus} \ \text{mut. } \alpha \\ &\qquad\quad ”\ \ \textit{speciosus} \;—\; ”\quad ”\quad ”\ \beta \\ &\qquad\quad ”\ \ \textit{cheehiel} \;—\; ”\quad ”\quad ”\ \gamma \end{aligned} \]

The evolution of these forms proceeded in the direction of development of the shell in breadth; the number of folds increased, and the latter became flatter.

On the basis of the study of the Siberian material I cannot agree with the authors cited, if only because Sp. cheehiel represents merely one of a fairly numerous set of forms, which it would be strange to regard as varieties of one species, Sp. speciosus, especially since some of them show greater similarity to other species. I also cannot agree that Sp. cheehiel is characterized by very narrow spaces between the folds and by the number of the latter—9–10 on each side of the fold and sinus (8, 317); the extensive material at my disposal permits me to assert that precisely these elements of the sculpture are subject to strong individual variability. Indeed, in the Siberian representatives of Sp. cheehiel and other spe...

of this group—6–7 folds on each side of the saddle and sinus occur just as often as 9–10; the width of the intervals between the folds also varies.

Our spirifers show great similarity to a number of Lower Devonian (Coblenzian) forms. This similarity is especially great when we have internal molds, and in this case the indication by Fromaget and Sautin of the possibility of erroneous identifications¹ (8, 317) is quite appropriate. For example, in pl. III, figs. 14, 15, 20, 22, photographs are given of Korgon and North Altai representatives of Sp. cheehiel, var. altaica, and a copy of Drevermann’s drawing of Sp. primaevus. Also undoubtedly close to our spirifers is the Indochinese Spirifer tonkinensis; there are close forms also in the Lower Devonian of Siberia: these are, first of all, the group Sp. korovini from the Altai $D_1^2$ (18). I am not able at present to indicate a direct ancestor of our group among these Lower Devonian forms. As for the Eifelian fauna, here, apparently, a solution is possible, and it will be precisely the one proposed by Fromaget and Sautin.

Sp. speciosus differs from the spirifers of the Sp. cheehiel group by its smaller size, lesser development in width, and smaller number of folds (3–4 on each side of the saddle and sinus). If one traces from this standpoint the individual development of a representative of the Sp. cheehiel group, one can see confirmation of this supposition: young specimens of Sp. cheehiel possess a smaller number of ribs and a more isometric shell (pl. IV, figs. 24–26).

Nor does the horizontal distribution of Sp. speciosus contradict this supposition regarding the origin of the Sp. cheehiel group: Fromaget and Sautin indicate its presence in Indochina; there are, it is true, old indications of the presence of this species also in the Altai (32, 72, 73, 78). That this is possible is confirmed by the abundance of European Eifelian forms in the Devonian fauna of Siberia, the evidence for which was given above.

Thus, the origin of the Spirifer cheehiel group may be imagined in the form of the following hypothesis: during the dispersal of the European Eifelian fauna into Asia, Spirifer speciosus penetrated together with it into the Kuznetsk–Altai basin; in Givetian time this basin was isolated from the western ones, and under these conditions of isolation a local group of forms arose from Sp. speciosus, which in a short time attained extraordinary flourishing and conquered the South Chinese basin, whereas in its homeland Sp. speciosus was displaced by other forms of brachiopods and became extinct toward the end of the Eifelian epoch, when such newcomers as Str. burtini and Unc. gryphus appeared in enormous numbers in the Devonian sea².

Having accepted such a solution to the question of the genesis of the Sp. cheehiel group, it is natural, further, to pose the question of its subsequent development already in Upper Devonian time. The factual material bearing on this question is as follows. As was already noted above, Tyzhnov found small representatives of the Sp. cheehiel group in the lower beds of $D_3$ on the northern margin of the Kuzbass. No other group of spirifers that could be genetically linked with the Sp. cheehiel group can be indicated in the Upper Devonian. Such forms as Spirifer laevigatus Roem. in Europe and Spirifer sublaevigatus Loss. in the Kuzbass possess only certain, purely external features of similarity to the Sp. cheehiel group and, to a much greater extent, features of difference. At the same time, the Lower Frasnian fauna of Siberia is well known to us. This gives every reason to conclude that the Spirifer cheehiel group, in the main,

became extinct by the beginning of the Upper Devonian, in connection with a change in the conditions of existence, which entailed a fairly clearly expressed general renewal of the fauna (the appearance in large numbers of representatives of the genus Anathyris Peetz, of the Spirifer disjunctus group, etc.).

This assumption is also fully consistent with theoretical considerations. Indeed, we have already seen that, during the short time of its existence, the group Sp. cheehiel attained an extraordinary flourishing, producing a large number of forms, including such forms as display extreme degrees of specialization, for example Sp. mirabilis and Sp. cultrijugatifоrmis. It is quite natural to suppose that, with the change in the conditions of existence at the end of the Middle Devonian, this highly specialized group was unable to adapt to them and was forced to leave the stage; only a few, dwindling and oppressed epigones of this group persisted for some time at the beginning of the Upper Devonian, but were quickly and completely displaced by other groups of animals.

In such outlines do the genetic relations of the Spirifer cheehiel group with other groups of spirifers appear to me, insofar as we can judge these relations from the data currently available.

On the species Spirifer (Hysterolites) mirabilis Khalfin

This species, interesting as an expression of the extreme specialization of the Sp. cheehiel group, was established by me (19) on the basis of only one specimen, though a well-preserved one, from the Lebedyanian Devonian (pl. II, fig. 8a, b). While examining paleontological material from old collections preserved in the cabinet of historical geology of the Tomsk Industrial Institute named after S. M. Kirov, I found a piece of yellowish-gray calcareous rock, from which it proved possible to prepare three specimens belonging to the species Sp. (Hyst.) mirabilis. One specimen is a completely preserved shell (the end of the tongue of the sinus is broken off); it is shown in fig. 10a–b of pl. II; the second specimen is a shell obliquely cut off from the anterior and lateral margins; and, finally, the third specimen is a well-preserved dorsal valve. The limestone from which these specimens were obtained comes from the upper reaches of the Ya River, but its exact locality is unknown. This material makes it possible to establish considerable variability in certain external characters of the species Sp. (Hyst.) mirabilis and to make the following additions to the characterization of this species:

1. The cardinal angles of the shell are drawn out into long pointed extremities, in some specimens distinctly delimited from the lateral margins by a corresponding notch on the latter; in other cases the lateral margins pass smoothly into the pointed extremities.

2. The cardinal angles in the Lebedyanian specimen are separated from the convex surface of the ventral valve by distinct depressions; these depressions are still more sharply expressed in one of the specimens from the Ya River, being developed both on the ventral and on the dorsal valve (pl. II, fig. 10a); in the two other specimens this character is not expressed.

3. Both valves are moderately convex, but the strongly upturned saddle creates the impression of great convexity of the shell as a whole; the ratio of width to length is about 3.

4. The sinus is very wide and deep; the tongue is extremely strongly developed, though apparently not always to the same degree as in the Lebedyanian specimen; thus, a slight swelling in the anterior part of the sinus may be absent.

5. The saddle is very high, narrow, sharp-topped, roof-shaped; it looks especially sharp on internal molds. The width of the saddle near the anterior margin is equal to the width of \(2\frac{1}{2}\)—3 adjacent ribs and is almost half the width of the sinus.

1. The radial folds are sharp and high, but rounded; the intervals between them are as broad and rounded as the folds themselves. The number of folds is 6–7 on each side of the saddle and sinus; an eighth is sometimes faintly indicated. The fine details of the sculpture are exactly the same as in the other representatives of the group.

2. On the internal molds the muscular tubercles¹ are strongly developed, oval in outline, and bear a shallow, flat longitudinal depression corresponding to the sinus.

The remaining characters of the species Sp. (Hyst.) mirabilis are shared with Sp. (Hyst.) cheehiel. Despite the variations noted above in some characters, this species is nevertheless, on the whole, clearly characterized and sharply distinguished from the other representatives of the group Spirifer cheehiel.

The closest forms are Spirifer (Hysterolites) cheehiel var. alata and, in some respects, Spirifer (Hysterolites) cultrijugatifofmis. The first form is readily distinguished, if a dorsal valve is available, by the character of the saddle, which in the variety alata is as rounded as in Sp. (Hyst.) cheehiel typ.; isolated ventral valves are more difficult to distinguish, but the sinus in Spirifer (Hysterolites) cheehiel alata is less developed than in Spirifer (Hysterolites) mirabilis and is flatter; moreover, in the former form there are no depressions separating the cardinal angles from the rest of the surface of the ventral valve. Sp. (Hyst.) cultrijugatifofmis approaches Sp. (Hyst.) mirabilis in its high roof-shaped saddle and in the extraordinary development of the sinus, as well as in the character and number of ribs. Distinguishing features are the absence in Sp. (Hyst.) cultrijugatifofmis of long cardinal points, the greater convexity of the valves and of the shell as a whole, and the broader saddle.

Sp. (Hyst.) mirabilis is so far known only from the northern margin of the Kuzbass. However, in the Givetian deposits of the Northern Altai (Malafeev spring) there are specimens, in the form of internal molds, that closely recall this species. The molds of the dorsal valves are especially similar to it in their narrow and sharp-crested saddle. But, taking into account a certain deformation of these specimens, I cannot identify them with Sp. (Hyst.) mirabilis, since a similar character of the saddle may have arisen as a result of secondary (mechanical) effects. In addition, the molds of ventral valves associated with these specimens possess bipartite muscular tubercles (pl. III, figs. 13–15), and impressions of the external surface of the valves found there differ in no way from Spirifer (Hysterolites) cheehiel typ.

In the limestone sample from the Ya River, from which the above-characterized specimens of Sp. (Hyst.) mirabilis were obtained, the following were found together with the latter: Atrypa reticularis, Atrypa sp., Spirifer (Hysterolites) cheehiel typ., Cyrtina heteroclita, Schellwienella umbraculum?, Productella sp., Chonetes cf. subcancellata, crinoid columnals, and Fenestellidae.

On the Givetian Basin of Siberia

Corrections to already-made paleogeographic reconstructions must be introduced continuously, since such reconstructions are the most important auxiliary material in the study of the history of the earth.
Diener. Principles of Biostratigraphy, p. 124, 1934.

In the preceding account I have already had occasion in several instances to touch upon questions of the Givetian geography of Eurasia. This was done only to the extent that the introduction of elements of paleogeography was necessary for clarifying one or another question concerning the group Spirifer cheehiel. But,

On the other hand, the data presented above on the distribution of the group Sp. cheehiel and on its relationship to other groups of fossils make it possible to express also certain special considerations concerning the Givetian history of Siberia. True, in passing to these broader questions we immediately encounter a number of difficulties, caused by the insufficient study of the Devonian deposits of certain regions. First of all, it is necessary to note the absence of a description of the fauna of Kazakhstan and the complete lack of study of the rich and interesting Devonian fauna of the Kamensk region on the Ob River. Nevertheless, I consider it useful to draw those conclusions regarding the paleogeography of the Givetian epoch in Siberia which follow from the preceding exposition.

Let us summarize the propositions set forth above in various places in this article:

1. In the Givetian fauna of the Minusinsk–Kuznetsk–Altai region there is a large number of European forms, but all of them, with very rare exceptions, belong to species distributed also in lower horizons of the Devonian. Along with this, in the Givetian fauna of the indicated region there are absent the Givetian cosmopolitans—Stringocephalus burtini and Uncites gryphus—but there is a large number of native forms, in particular the group Spirifer cheehiel. On this basis the conclusion is drawn that the Minusinsk–Kuznetsk–Altai basin in the Eifelian epoch had communication with the Turkestan–Ural basin, whence the European fauna migrated into it, but in the Givetian epoch this Siberian basin was isolated from the western ones and was populated by a fauna that was native and inherited from the Eifelian epoch.

2. On the basis of the presence in the Kuznetsk–Altai and South Chinese basins of the characteristic group Spirifer cheehiel and of its absence in the Turkestan basin, it is accepted that between the Kuznetsk–Altai and South Chinese basins in Givetian time the communication was direct, and not circuitous through Turkestan, as some authors imagine.

3. The presence in the South Chinese basin of Str. burtini alongside Spirifer cheehiel indicates a connection of this basin with the Turkestan one, in contrast to what has been established in this respect for the Kuznetsk–Altai basin. The circumstance that Str. burtini did not penetrate from the Chinese basin into the Kuznetsk–Altai one permits the supposition that in the Givetian epoch the migration of fauna in Asia took place mainly from north to south, from the Kuznetsk–Altai basin into the Chinese one. This supposition could acquire the character of certainty, or a different solution of the question would be required, if I had the opportunity to obtain precise information on the stratigraphic position of the group Spirifer cheehiel in China and to compare it with that in Siberia.

At present it is very difficult to trace the eastward extent of the Siberian Givetian basin, owing to the extreme fragmentary nature of our information about the Devonian deposits of these regions and the complete lack of study of their fauna¹. At various points east of Lake Baikal, Devonian, in particular Middle Devonian, deposits have been recorded as far as the Lesser Khingan, but the brief faunal lists, usually with extremely approximate determinations of the forms, often render conclusions as to the age of the corresponding deposits not very convincing; scattered information on the Devonian deposits of this vast territory has been compiled by Krishtofovich (24, 82–85). Of great interest is the—

the occurrence in the Devonian deposits of the Lesser Khingan of Spirifer medialis Hall, this characteristic form of the upper \(D_2\) of North America: Spirifer medialis is extraordinarily close to Sp. martianoffi, one of the most widespread forms of our cheehiel fauna, and as early as 1887 Chernyshev asserted (48, 137) that these forms are indistinguishable from one another. If one takes into account that in the Siberian cheehiel fauna North American forms are fairly common, including such forms as Productella spinulicosta Hall, Rhipidomella vanuxemi Hall, Schuchertella chemungensis Conr., Athyris fultonensis Swall., which appear only from the second half of \(D_2\), then the existence, in the Givetian epoch, of a connection between the Kuznetsk–Altai basin and the sea of North America becomes very probable, especially since from the Middle Devonian onward there already existed the Mongolian geosyncline, which possibly reached the Pacific Ocean (23, 269).

The western boundary of the Givetian basin can be determined with greater precision than the eastern one, owing to the fact that for the geology of Kazakhstan we have a number of major works, including Kassin’s detailed summary (14). Despite the general facies instability of the Devonian (in particular, Middle Devonian deposits) of Kazakhstan, the general regularity of their change in passing from east to west is nevertheless expressed quite clearly. If in the Bayan-Aul district we have normal marine rocks of Givetian age, represented by sandstones with interbeds of limestones with a rich and diverse fauna, then in more western regions this character of the Givetian deposits is gradually lost, and already in the Akmolinsk and Kokchetav districts variegated and brightly colored sandstones with plant remains predominate in the Middle Devonian sequence, while limestones with Givetian fauna occur within them only sporadically. Still farther west, as one approaches Ulu-Tau, marine deposits within \(D_2\) disappear completely, and this division of the Devonian proves to consist exclusively of red and brown continental sandstones. Here the shore of the Givetian basin and that landmass whose position was defined by Kassin (14, 34) are outlined quite clearly. Just as definitely established is the presence of land in the Balkhash region throughout the entire Devonian (14, 29).

The Devonian fauna of northeastern Kazakhstan has not been described; the sufficiently detailed lists of forms given in the literature draw attention, above all, by the absence from them of Str. burtini and Unc. gryphus. It is permissible to think that these species have not been found in Kazakhstan, since even preliminary identifications would have noted the presence of these common and stratigraphically so important forms.

Therefore there is every reason to believe that the ancient massif of Ulu-Tau and the Balkhash region were parts of a single continental barrier that separated the Givetian basin of northeastern Kazakhstan from the Uralian and Turkestan basins. The continuation of this barrier to the south and east cannot be traced with the same certainty, but in any case, south of Balkhash, in the Ili basin, a reliably marine, faunistically characterized Middle Devonian has not been established (16, 12), while in the Tarbagatai the Middle Devonian deposits differ in the western and eastern parts of the range: whereas in the eastern Tarbagatai the Givetian stage is represented by marine deposits with Spirifer mucronatus, in the western part of this range the Givetian deposits apparently consist of continental red, barren sandstones, conglomerates, and quartzites with effusives (14, 31). It should be noted that although on Grabau’s paleogeographic map of the Givetian epoch (10, 161) a connection between the Kuznetsk–Altai and Turkestan basins is shown, in the text this author expressed doubt as to the existence of this connection between the basins (ib., 161).

Returning to the composition of the Givetian fauna of northeastern Kazakhstan,

we must note one further circumstance: in the lists of forms cited by various authors, Sp. cheehiel is absent. I know only of an indication of the presence in the Devonian deposits of the upper reaches of the Chiderty River of Spirifer cf. speciosus (27, 35), which might prove to be a spirifer from the Sp. cheehiel group, and also Chernyshëv’s remark in his Devonian (49, 104) that Sp. cheehiel “occurs both in the Altai and in the Kirghiz Steppe.” But it can hardly be admitted that the Sp. cheehiel group, as a rule, was passed over in silence if it played in the Kazakh Devonian the same outstanding role as in the Siberian. Alongside this, in the Kazakh Middle Devonian there is a considerable number of forms common with the Givetian fauna of Siberia, including such a widespread form as Spirifer martianoffi (= Sp. audaculus). This species is also present in the Middle Devonian of the eastern part of Tarbagatai; the fauna of the latter, in general, has been little studied; there are no indications whatever of the presence in it of Sp. cheehiel, or likewise of Str. burtini, unless one counts Vasilevsky’s extremely indefinite report of an “internal cast, somewhat resembling Str. burtini,” together with Spirifer sp., Atrypa reticularis, and Dalmanella sp. (50, 1071).

Until a description of the Kazakh fauna has been published, there is no possibility of entering into the details of a comparison between this fauna and the Siberian fauna; but the known difference between them is already at present revealed quite definitely, and this compels one to assume the presence of some barrier that impeded the free exchange of faunas between the Kazakh and Siberian basins in Givetian time. I have no grounds for entering into a discussion of the character of this barrier—it is quite possible that it was a deep sea within the Semipalatinsk–Kalbin geosyncline established by the most recent investigations (31, 9)—but the existence of this barrier is suggested by the differences in the composition of the Kazakh and Siberian Givetian faunas, despite the great similarity in the facies character of the corresponding basins¹.

Regarding the latter circumstance, the following must be specially noted. When one reads about the changes in the facies character of the Givetian deposits as one approaches from the east the Kokchetav region and Ulu-Tau (14, 24, 27), one is struck by the great similarity to what has been established much farther to the east, where the Givetian basin washed the northern end of the Kuznetsk Alatau island (46): the same sequence of red-colored rocks with plant remains; likewise, at a number of points it is underlain by effusives; the same repeated fluctuations of sea level; and finally, the same interbeds of carbonaceous shales and coals in the mucronate beds, i.e. in beds stratigraphically equivalent to the beds with Sp. cheehiel in the Kuzbass and, consequently, equivalent to the Barzas productive series. This coincidence of geological setting obviously has not only theoretical but also practical interest.

The question remains unresolved as to how the connection was effected between the Minusinsk–Kuznetsk–Altai basin and southeastern China. Grabau (10, 162) wrote of the existence of this connection between the Givetian basins of Siberia and China on the basis of facts known to him concerning the occurrence of Sp. cheehiel in the Minusinsk depression and on the Ya River north of

Kuzbass. However, the factual material on the basis of which one could indicate the position of the strait connecting these two basins is lacking—that is, deposits with the fauna of Sp. cheehiel have not yet been established within Mongolia and Central China. It is known that in the Uryankhai depression there is a Devonian development, lithologically similar to the Minusinsk Devonian and represented by all three divisions; however, the fauna of these Devonian deposits, the discovery of which was reported in the literature 30 years ago (34, 9), has still not been described and has not even been presented in the form of lists; a summary of the materials of interest to us for the Uryankhai depression is available in Bazhenov (3, 64–66).

Over the vast territory of the Gobi, reliably established, faunistically characterized Devonian deposits have still not been found. And although in the geological report of the Third Asiatic Expedition there is a report that at the foot of the Gurvan-Saikhan range a piece of red limestone was found with fragments of brachiopod shells and crinoid ossicles of Devonian or Carboniferous age (4, 255), nevertheless the authors of this report fully retain their former point of view, namely that the Paleozoic group is poorly distributed within the Gobi and was hardly ever represented by formations older than the Mississippian (4, 406). Thus, the Gobi continent in Devonian time separated the Kuznetsk–Altai basin from the seas of southern China, and its presence serves as an obstacle to drawing a strait that connected these basins in Givetian time.

However, this question cannot be considered finally resolved until the question of the age and conditions of formation of the graywacke-argillite series (the Khangai series of Berkey and Morris), which is exceptionally widespread in Mongolia, has been resolved. A number of authors assign a Precambrian age to this series, but recently more and more indications of its younger age have appeared. Chaikovskii gives convincing evidence for the presence of Carboniferous deposits within this series (47, 37). In Lebedeva’s work on the geology of the Gurvan-Saikhan mountain group, the supposition is expressed that this series is of Middle Paleozoic age (25, 60).

Without entering into discussion of this problem, and in particular of the conditions of formation of the graywacke-argillite series of Mongolia, I shall recall only the following very important discoveries: first, at the foot of the Gurvan-Saikhan, in proluvial deposits, both the Third Asiatic Expedition of 1922–23 (4, 255) and the Mongolian Expedition of the Academy of Sciences of the USSR in 1931 found pieces of red limestone with undoubtedly marine fauna (Brachiopoda, Coelenterata, Crinoidea, etc.) of Devonian or Carboniferous age; second, according to Lebedeva, although mute, lithologically identical red limestones are included in the graywacke-argillite series of Gurvan-Saikhan.

In the case of a Middle Paleozoic age for the graywacke-argillite series, within this extraordinarily thick sequence (20,000 feet according to the determination of Berkey and Morris) there would quite possibly be a place also for deposits of Givetian age. In that case, one could speak of a broad connection between the Siberian and South Chinese basins in the Givetian epoch, which would best explain the similarity of their faunas and would confirm Grabau’s suggestion of their connection. The resolution of this question evidently belongs to future investigations.

Conclusion

The article presents the vertical and horizontal distribution of representatives of the Sp. cheehiel group in Siberia, gives brief characteristics of the individual species included in this group, provides a diagnosis of the group as a whole and a general characterization of the Givetian fauna of Siberia, and, on the basis of all these materials, offers considerations concerning the paleogeography of Siberia in the Givetian epoch.

The Sr. cheehiel group occupies in Siberia a quite definite stratigraphic position, being the guide group for the Givetian stage. In facies terms the group is characterized by a broad distribution: the spirifers of this group lived at various depths—from the coastal surf zone to the considerable depths of the zone of solitary corals and, apparently, deeper. But they attained their maximum development in shallow marine zones. Within this group the following nine forms are known, brief characteristics of which are given in the appended table:

Spirifer (Hysterolites) cheehiel Kon. typ.
Spirifer (Hysterolites) cheehiel Kon., var. alata Stuck.
Spirifer (Hysterolites) cheehiel Kon., n. var. altaica.
Spirifer (Hysterolites) mesolobus Kotovin
Spirifer (Hysterolites) semicostalis Khalf.
Spirifer (Hysterolites) bidevexus Khalf.
Spirifer (Hysterolites) mirabilis Khalf.
Spirifer (Hysterolites) cultrijugatiforinis n. sp.
Spirifer (Hysterolites) orthogonalis Khalf.

Within the Givetian fauna of Siberia this group enjoys widespread distribution, alongside a large number of other endemic forms (Sp. martianoffi Stuck., Sp. schmidti Stuck., Emanuella takwanensis Kays., Athyris subacuminata Khalf., etc.). The abundance of endemic forms in the Givetian fauna of Siberia is combined with a large number of European forms. The latter, however, with very rare exceptions, are not guide Givetian forms, but existed earlier as well. At the same time, the Middle Devonian fauna of Siberia lacks the Givetian cosmopolitans—Stringocephalus burtini and Uncites gryphus, widely distributed in Europe and Central Asia. From these factual data the conclusion is drawn: in Givetian time the Siberian basin was isolated from the Ural and Central Asian basins, and was inhabited by an endemic fauna inherited from the Eifelian epoch, when this isolation did not exist.

From a comparison of the distribution of Str. burtini and Sp. cheehiel the conclusion is drawn that two faunas existed in parallel within Eurasia during the Givetian epoch—the stringocephalus fauna and the cheehiel fauna. In pure form the first inhabited the basins of Europe, the Urals, Western and Central Asia, while the second inhabited the Minusinsk–Altai–Kuznetsk basin and, possibly, more eastern basins connected with the Mongolian geosyncline. In the South Chinese basin these faunas were mixed, which proves that during the Givetian epoch this basin was connected with the Central Asian and Minusinsk–Kuznetsk–Altai basins. The fact that in the South Chinese Givetian basin there existed Str. burtini and Sp. cheehiel, while the former did not penetrate (at least in significant numbers) into Siberia, and the latter did not penetrate into Turkestan, makes it possible to suggest that in the Givetian epoch the principal directions of faunal migration in Asia were from north to south and from west to east.

In the chapter on the systematic position and genetic relationships of the Sp. cheehiel group, a detailed diagnosis of this group is given and in detail—

the internal skeleton has been described; in particular it has been established that, in representatives of this group, the spondylium and the calcareous ribbon forming the brachial spirals are hollow. Representing a natural association of forms, united stratigraphically and geographically and possessing a number of internal and external features, the group Sp. cheehiel deserves to be singled out as an independent systematic unit; the author refrains from doing so only because it is impossible to become acquainted in detail with the nearest European and American forms. Therefore the spirifers of the Sp. cheehiel group are provisionally assigned to the subgenus Hysterolites, to which they are closest in external characters.

Among the Lower Devonian forms there are many very close to the spirifers of the Sp. cheehiel group, but at present it does not appear possible to indicate among them a direct ancestor of this group. Of the Eifelian forms, the closest, as has already been noted in the literature and above, are the European Sp. speciosus and the American Sp. duodenarius. The origin of the Sp. cheehiel group may be represented as follows: together with the rest of the European fauna, Sp. speciosus penetrated into Siberia in the Eifelian epoch. In the Givetian epoch this species in the west was displaced by other groups of animals, while in Siberia, under conditions of isolation from the Givetian immigrants (Str. burtini and others), this species gave rise to the Sp. cheehiel group, which in a short time attained an extraordinary flourishing and occupied the Siberian and South Chinese basins. The origin of the Sp. cheehiel group from Sp. speciosus is also confirmed by changes in the individual development of representatives of Sp. cheehiel. In the Upper Devonian fauna there are no forms that could be considered descendants of the Sp. cheehiel group, but there are indications of the presence, in the very lowest horizons of the Frasnian stage, of small and rare representatives of this group. The Sp. cheehiel group, over a short interval of time, reached its flourishing and, in some forms, an extreme specialization (Sp. mirabilis, Sp. cultrijugatiformis), but with a change in the conditions of existence it had almost completely died out by the beginning of the Frasnian epoch. The last, oppressed representatives persisted for a short time at the beginning of the Upper Devonian, but were displaced without trace by other groups of the renewed fauna.

In the last chapter, questions of the Givetian geography of Asia are touched upon. The western shore of the Siberian Givetian basin is outlined from Ulu-Tau to the Balkhash region and farther eastward—to western Tarbagatai. This shore was, apparently, an isthmus connecting the West Siberian continent (Tobolskia according to Grabau) with the West Chinese one (Tibetia according to Grabau) and separating the Siberian basin from the basin of Central Asia. Within the Siberian basin two regions are indicated, populated by different faunas: the Minusinsk–Kuznetsk–Altai region, for which the presence of the Sp. cheehiel group and the absence of Str. burtini and Unc. gryphus are characteristic; and northeastern Kazakhstan, in whose Givetian fauna, apparently,¹ all three of these forms are absent, but there is a series of species in common with the Kuznetsk–Altai region; this indicates that the exchange of fauna between these regions was hampered by some obstacle, which may have been a deep sea within the Semipalatinsk–Kolbino geosyncline recently established by Nekhoroshev and Gornostaeva.

The continuation of the Siberian basin eastward is traced with difficulty because of the incompleteness of our knowledge of the Devonian deposits of these territories, but nevertheless Givetian deposits have been recorded at a number of localities as far as the Lesser Khingan, and therefore there is no basis for denying the existence—

¹ The Devonian fauna of Kazakhstan has not been described, but in the literature there are a number of lists of Devonian brachiopods from this region.

Classification table of representatives

subgenus Hysterolites in the Siberian Devonian.

...the existence of the Mongolian geosyncline of Grabau. If this geosyncline reached the Great Ocean, it could have been the route by which elements of the American fauna, established in the Givetian fauna of Siberia, penetrated into the Siberian basin. But from all that has been set forth above it follows that this geosyncline could hardly have served as a conduit for Str. burtini into North America, where it penetrated by some other routes.

The existence of a direct connection between the Siberian and South Chinese basins in Givetian time cannot be doubted, unless one makes the improbable assumptions of a polyphyletic origin of the group Sp. cheehiel or of an incorrect identification of the Siberian and Chinese forms (Spirifer cheehiel, Atrypa sinensis, Em. takwanense). But where and how this connection was effected can hardly be decided at present. However, in Lebedeva’s most recent work on the geology of the Gurban-Saikhan mountain group, an extremely interesting suggestion is made concerning the possible Middle Paleozoic age of the graywacke-argillite formation which is exceptionally widespread in Mongolia and to which a Precambrian age is usually assigned. And if one compares with this the fact that, at the foot of the Gurban-Saikhan, pieces of red limestones with an indeterminate but unquestionably marine¹ Devonian or Carboniferous fauna were found, and that limestones analogous in lithological character, according to Lebedeva, form part of the graywacke-argillite series of the Gurban-Saikhan, then the question of the connection in Devonian time of the basins that interest us appears in an entirely new light. In this case, in place of part of the continent Gobia in Givetian time there might have been a broad strait separating the Tibetan and Chinese (Cathaysia according to Grabau) continents.

Thus, on the basis of an analysis of the cheehiel fauna, the following corrections to Grabau’s paleogeographic map (10,160) could be proposed: the presence of an isthmus between the continents Tobolskia and Tibetia, separating the basins of the Mongolian geosyncline from the Central Asian basin, and the presence of a strait which separated the continents Tibetia and Cathaysia and connected the seas of the Mongolian and Himalayan geosynclines.

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20. Peetz, G. Materials toward the knowledge of the fauna of the Devonian deposits of the margins of the Kuznetsk coal basin. Trudy geologicheskoi chasti kabineta, vol. IV. 1901.

21. Peetz, G. Devonian deposits. Yearbook on the Geology and Mineralogy of Russia, vol. III, section III. 1898.

22. Pilipenko, P. Mineralogy of Western Altai. Izvestiya Tomskogo Universiteta, XII. 1915.

23. Radugin, K. V. Middle Devonian Coelenterata of the environs of the village of Lebedyanskii in Kuzbass. (Manuscript).

24. Reed. Devonian Faunas of the Northen Shan States. Pal. Indica, N. S., v. II, mem. N 5. — 1908.

25. Schlotheim. Die Petrefactenkunde auf ihrem jetzigen Standpunkte durch die Beschreibung seiner Sammlung versteinerten und des Thier und Pflanzenreichs der Vorwelt erläutert. 1820.

26. Schlotheim. Nachträge zur Petrefactenkunde. 1822.

27. Sheiman, I. M. Trepostomata from the Middle Devonian of Minusinsk District, Yenisei Province. Izvestiya Geologicheskogo Komiteta, vol. 44. 1927.

28. Scupin, H. Die Spiriferen Deutschlands. Pal. Abh. v. Dames und Koken, Bd. VIII, Ht. 3. 1900.

29. Stuckenberg, A. Mater. z. Kenntn. d. Fauna d. devonisch. Ablager. Sibiriens. Trudy SPb. Akademii Nauk, series VII, vol. XXXIV, No. 1. 1986.

30. Tyazhnov, A. V. Materials on the stratigraphy and tectonics of the Devonian deposits of the southeastern margin of Kuzbass. Izvestiya Zapadno-Sibirskogo Geologo-Razvedochnogo Upravleniya, vol. XI. 1931.

31. Tyazhnov, A. V., Finkelshtein, M. M. and S. M. Shkorbatov. Materials on the geology of the Barzas region of the Kuznetsk coal basin. (Manuscript).*

32. Chaikovskii, V. K. New data on the geology of the central part of the Mongolian People’s Republic. Problemy Sovetskoi Geologii, No. 1. 1935.

33. Chernyshev, F. N. Fauna of the Middle and Upper Devonian of the western slope of the Urals. Trudy Geologicheskogo Komiteta, vol. III, No. 3. 1887.

34. Chernyshev, F. N. Historical geology. Devonian. 1925.

35. Vasil’evskii, M. M. On the geology of Tarbagatai. Izvestiya Geologicheskogo Komiteta, vol. 33. 1914.

36. Venyukov, P. N. Geological description of the southeastern quarter of the 14th sheet of row VII of the ten-verst map of Tomsk Province. Trudy geologicheskoi chasti kabineta, vol. II, issue I. 1896.

Explanations of the Plates

Plate I.

Fig. 1 a–c. Spirifer (Hysterolites) cheehiel Kon. typ. Reduced. Kuzbass, village of Lebedyanskoye.
Fig. 2 a–b. Spirifer (Hysterolites) bidevexus Khalf. Natural size. Kuzbass, village of Lebedyanskoye.
Fig. 3. Spirifer (Hysterolites) mesolobus Kog. Natural size. Kuzbass, village of Lebedyanskoye.
Fig. 4 a–d. Spirifer (Hysterolites) semicostalis Khalf.; a—natural size, b–d—reduced. Kuzbass.
village of Lebedyanskoye.
Fig. 5. Idem. Natural size.

Plate II.

Fig. 6. Spirifer (Hysterolites) cheehiel Kon. typ. Natural size. Southeastern Altai.
Fig. 7. Spirifer (Hysterolites) semicostalis Khalf. Natural size. Southeastern Altai.
Fig. 8 a–b. Spirifer (Hysterolites) mirabilis Khalf. Natural size. Kuzbass, village of Lebedyanskoye.
Fig. 9 a–b. Spirifer (Hysterolites) orthogonalis Khalf. Natural size. Kuzbass, village of Lebedyanskoye.
Fig. 10 a–b. Spirifer (Hysterolites) mirabilis Khalf. Natural size. Kuzbass, R. Yaya.
Fig. 11, 12. Spirifer (Hysterolites) cheehiel Kon. typ. Enlarged; character of the sculpture. Minusinsk basin, village of Beyskoye.

Plate III.

Fig. 13, 14, 15. Spirifer (Hysterolites) cheehiel Kon., n. var. altaica. Natural size; internal casts of ventral valves. Northwestern Altai, Malafeev spring.

Fig. 16, 17, 18. Spirifer (Hysterolites) cheehiel Kon. typ. Natural size; internal casts of ventral valves. Kuzbass, village of Lebedyanskoye.

Fig. 19. Spirifer (Hysterolites) cheehiel Kon. typ. Natural size; inner surface of the ventral valve. Kuzbass, village of Lebedyanskoye.

Fig. 20. Spirifer (Hysterolites) cheehiel Kon., n. var. altaica. Natural size; internal cast of a ventral valve. Western Altai, Korgon Range.

Fig. 21. Spirifer (Hysterolites) cheehiel Kon. typ. Natural size. Western Altai, Korgon Range.

Fig. 22. Spirifer primaevus Stein. Copy after Drevermann: Palaeontographica, Bd. L, Taf. XXIX, Fig. 4.

Plate IV.

Fig. 23. Spirifer (Hysterolites) cheehiel Kon., n. var. altaica. Natural size; internal cast of a ventral valve. Northwestern Altai, Malafeev spring.

Fig. 24, 25, 26. Spirifer (Hysterolites) cheehiel Kon. typ. Natural size; juvenile specimens. Kuzbass, village of Lebedyanskoye.

Fig. 27. Spirifer (Hysterolites) cheehiel Kon., n. var. altaica. Natural size. Northwestern Altai, R. Tikhaya.

Fig. 28. Spirifer (Hysterolites) mesolobus Kog. Natural size. Southeastern Altai.

Fig. 29. Spirifer (Hysterolites) cheehiel Kon. typ. Enlarged; character of the area and delthyrium. Minusinsk basin, village of Beyskoye.

Fig. 30. Idem. Restoration.

Fig. 31–32. Spirifer (Hysterolites) cheehiel Kon. typ. Natural size; brachial supports. Kuzbass, village of Lebedyanskoye.

Plate V.

Fig. 33 a–b. Spirifer (Hysterolites) cheehiel Kon. typ. Transverse sections of the umbonal part of the shell; × 2. Minusinsk basin, village of Beyskoye.

Fig. 34. Spirifer (Hysterolites) bidevexus Khalf. Natural size; the most inflated specimen. Kuzbass, village of Lebedyanskoye.

Fig. 35 a–e. Spirifer (Hysterolites) cultrijugatiforrnis n. sp. Natural size. Southeastern Altai.

Fig. 36. Spirifer cultrijugatus Roem. Copy after Schnur: Palaeontographica, 1853, Taf. XXXIII, Fig. 1e.

Plate I
To the work of L. L. Khalfin

Fig. 1
a
b
c

Fig. 2
a
b

Fig. 3

Fig. 4
a
b
c
d

Fig. 5

Plate II

To the work of L. L. Khalfin

Fig. 6

Fig. 11

Fig. 7

Fig. 8

Fig. 12

Fig. 9

Fig. 10

For the work of L. L. Khalfin

Table III

Fig. 13

Fig. 14

Fig. 15

Fig. 16

Fig. 17

Fig. 18

Fig. 20

Fig. 21

For the work of L. L. Khalfin

Table IV

Fig. 23

Fig. 24

Fig. 25

Fig. 26

Fig. 30

Fig. 27

Fig. 29

Fig. 28

Fig. 31

Fig. 32

To the work of L. L. Khalfin

Plate V

a  b

Fig. 33

Fig. 34

a

b

c

Fig. 35

a

e

Fig. 36

1. Fragments of brachiopods, corals, crinoid ossicles. ↩↩↩↩↩↩

2. The latter, even if it existed in the Eifelian epoch, occupied a wholly subordinate position. ↩